This invention is concerned with compositions that are applied to the axillae to deodorize and help keep the underarms dry. Conventional products that perform both functions are termed antiperspirants and employ astringents such as aluminum chlorhydrate or zirconium oxychloride aluminum hydroxychloride complex. They are believed to inhibit the production of perspiration by the sweat glands.
The compositions of this invention employ moisture absorbent materials to achieve at least part of the dryness effect. These materials are not drugs and do not affect the normal functioning of the sweat glands.
Moisture absorbent materials have been used in the past to help keep the underarms dry. Particularly noteworthy are GB 1,482,756 and U.S. Pat. No. 4,508,705. These prior art materials are water insoluble and absorb water to form non-tacky gels. Chemically, these materials are similar. They are anionic polyelectrolytes that have been cross-linked covalently or with metal cations having a valence of at least two. The exception noted are carboxypolymethylenes of GB 1,482,756. These are very high molecular weight anionic polyelectrolytes that have not been cross-linked.
In U.S. Pat. No. 4,659,564 it is mentioned that water absorbents of the prior art tend to suffer a reduction in their water absorbing capacity in the presence of electrolytes, including the ionic species present in sweat. Antiperspirant salts such as those based on aluminum and zirconium have a particularly strong adverse affect on water absorbents. U.S. Pat. No. 4,659,564 is concerned with the synthesis of new water absorbents that are resistant to such salts. In the example given, it is shown that a typical water absorbent, water-insoluble cross-linked sodium carboxymethyl cellulose, will lose 97% of its water-absorbency in the presence of aluminum zirconium hydroxychloride glycine complex, while their new synthetic polymer will only lose 57% of its water absorbency.
Most of the water absorbent materials of the prior art are synthetic polymers that have been prepared using reactive chemicals. The compositions are intended to be applied daily and kept on the skin 24 hours each day. Consequently, it is essential that these synthetic polymers be thoroughly purified to remove all traces of reactive chemicals. It is now recognized that traces of reactive chemicals can be quite insidious, taking years before the toxic effect is observed.
The cross-linked alginates and carragheenates of the prior art are natural materials that are recognized to be non-toxic. However, they lack heat stability. When compositions containing these polymers are maintained at 60.degree. to 79.degree. C. for many hours, as required for the manufacture of underarm sticks they discolor and suffer a loss of water-absorbing capacity.